A long term goal in our lab is to determine the structure-function scope of bPNA. The objective of this application is to use bPNA to produce fluorogenic aptamers that are function as theranostic tools for study and treatment of HER-amplified cancer. The central hypothesis of this application is that bPNA hybridization with nucleic acid libraries can be used to integrate fluorogen-photosensitizers into affinity selection such that the fluorogen is a component of the recognition site that makes close contact with the ERBB receptor. Target binding thus activates fluorescence and exposes the aptagenic site to maximum damage by fluorogen-produced reactive oxygen species. Our rationale for this hypothesis is the finding that bPNA triplex hybridization can fluorescently label DNA and RNA aptamers. Our independent efforts are supported by the shared resources and expertise of the Center for RNA Biology at the Ohio State University as well as collaborators in clinical investigation of HER+ breast cancer, ERBB receptor biochemistry, SELEX, photoimmunotherapy on ERBB-dysregulated cancer and photo physical methods. These factors combine to create a setting conducive to the successful completion of the proposed investigations. The proposed research is creative and original because a new general method is described using bPNA hybrid structures that will seamlessly incorporate non-native groups (fluorogens) into affinity selection. This will allow selection for artificial functional groups atthe aptamer-target recognition interface. The bPNA-aptamer hybrid structures offer transformative advantages not previously known. This creative, original approach will yield the following expected outcomes: 1) a widely applicable procedure for inclusion of prosthetic groups in SELEX; 2) fluorogenic reporters of HER2, HER3 and heterodimer status, as well as a general protocol to report on any aptagenic site; 3) aptamer- directed inactivation of HER2 and HER3 in vitro and in cell culture. The proposed research will yield theranostic fluorogenic aptamers for diagnosis and treatment of HER-amplified breast cancer as well as establish a general protocol for aptamer-directed biosensors and photodynamic therapeutic reagents.